Search

The paper studies the effect of adhesion and surface relief of laminated plywood on rubber friction. Samples of birch plywood are studied, the surfaces of which have different texture and roughness and are made on the basis of two different resins: phenol formaldehyde and melamine. The study of the static and dynamic friction coefficient is carried out on a tribometer according to the ring-disk contact scheme at room temperature of 23°C in the range of normal pressures from 0.1 to 0.5 MPa in dry and lubricated friction mode. The study of the adhesion properties of the coatings was carried out on an atomic force microscope with a 900 nm ball at the tip. The refined contact interaction model of the spherical tip with the plywood surface made it possible to estimate the surface energies of the coatings. The findings show that when using plywood in dry contact only, it is necessary, first of all, to increase the adhesion properties of its surface, for example by introducing filler-adhesives or using a polymer resin with increased adhesive properties as the base of the laminated coating. If it is assumed that liquids or contaminants enter the plywood surface during operation, then the best effect is the application of a two-level texture: deep dents to remove water from the contact area and surface roughness to increase adhesive properties. It should be noted that the roughness on some types of laminated films can change rapidly due to wear, therefore the use of films with increased adhesive properties is an advantage for increasing the adhesive properties of the surface of laminated plywood. [ABSTRACT FROM AUTHOR]

The coefficient of friction due to bulk viscoelastic losses corresponding to multiscale roughness can be computed with Persson's theory. In the search for a more complete understanding of the parametric dependence of the friction coefficient, we show asymptotic results at low or large speed for a generalized Maxwell viscoelastic material, or for a material showing power law storage and loss factors at low frequencies. The ascending branch of friction coefficient at low speeds highly depends on the rms slope of the surface roughness (and hence on the large wave vector cutoff), and on the ratio of imaginary and absolute value of the modulus at the corresponding frequency, as noticed earlier by Popov. However, the precise multiplicative coefficient in this simplified equation depends in general on the form of the viscoelastic modulus. Vice versa, the descending (unstable) branch at high speed mainly on the amplitude of roughness, and this has apparently not been noticed before. Hence, for very broad spectrum of roughness, friction would remain high for quite few decades in sliding velocity. Unfortunately, friction coefficient does not depend on viscoelastic losses only, and moreover there are great uncertainties in the choice of the large wave vector cutoff, which affect friction coefficient by orders of magnitudes, so at present these theories do not have much predictive capability. [ABSTRACT FROM AUTHOR]

We study the adhesion and friction for three tire tread rubber compounds. The adhesion study is for a smooth silica glass ball in contact with smooth sheets of the rubber in dry condition and in water. The friction studies are for rubber sliding on smooth glass, concrete, and asphalt road surfaces. We have performed the Leonardo da Vinci-type friction experiments and experiments using a linear friction tester. On the asphalt road, we also performed vehicle breaking distance measurements. The linear and non-linear viscoelastic properties of the rubber compounds were measured in shear and tension modes using two different Dynamic Mechanical Analysis (DMA) instruments. The surface topography of all surfaces was determined using stylus measurements and scanned-in silicon rubber replicas. The experimental data were analyzed using the Persson contact mechanics and rubber friction theory.

A multiscale finite element framework for the calculation of sliding rubber samples on rough surfaces is proposed. The two essential physical contributions hysteresis and adhesion are modelled. Hysteresis originating from the viscoelastic nature of rubber materials is included directly by incorporating the rough surface in the calculation with microscopic details and without transformations or a reconstruction of the surface. The adhesive interaction is introduced by a macroscopic shear stress law coupled to the hysteresis simulation by the evaluation of the relative contact area. The assumed mechanisms and the framework are explained in detail and are used to validate the method for experimental results of different materials for low sliding speeds. [ABSTRACT FROM AUTHOR]

We present a comprehensive investigation of the adhesive rubber-solid contact problem by analytical and numerical methods. Theories of rubber friction are reviewed and a new contact theory is developed. The adhesive contact problem is solved using the boundary element method. The introduction of adhesion leads to full coverage below a certain length scale. Friction coefficients are calculated from the spectral density of the rubber surface by splitting the numerical problem into two length scales. Adhesion is shown to increase friction at low velocities. The influence of filler is modeled by assuming that their size corresponds to a linear cross-over dimension separating the bulk elastomer from the composite. Finally, we discuss open problems and describe a simplified picture of rubber friction. • Adhesion increases low-velocity friction by increasing low-wavelength deformation amplitude. • Rubber has to be viewed as composite material at length scales relevant for friction. • Rubber's contour generally has a higher Hurst exponent than the substrate. • (Adhesion-induced) elastic instabilities probably determine friction at lowest velocities. [ABSTRACT FROM AUTHOR]

Since the early study by Grosch in 1963 it has been known that rubber friction shows generally two maxima with respect to speed—the first one attributed to adhesion, and another at higher velocities attributed to viscoelastic losses. The theory of Klüppel and Heinrich and that of Persson suggests that viscoelastic losses crucially depend on the "multiscale" aspect of roughness and in particular on truncation at fine scales. In this study, we comment a little on both theories, giving some examples using Persson's theory on the uncertainties involved in the truncation of the roughness spectrum. It is shown how different choices of Persson's model parameters, for example the high-frequency cutoff, equally fit experimental data on viscoelastic friction, hence it is unclear how to rigorously separate the adhesive and the viscoelastic contributions from experiments. [ABSTRACT FROM AUTHOR]

We study the adhesion and friction for three tire tread rubber compounds. The adhesion study is for a smooth silica glass ball in contact with smooth sheets of the rubber in dry condition and in water. The friction studies are for rubber sliding on smooth glass, concrete, and asphalt road surfaces. We have performed the Leonardo da Vinci-type friction experiments and experiments using a linear friction tester. On the asphalt road, we also performed vehicle breaking distance measurements. The linear and non-linear viscoelastic properties of the rubber compounds were measured in shear and tension modes using two different Dynamic Mechanical Analysis (DMA) instruments. The surface topography of all surfaces was determined using stylus measurements and scanned-in silicon rubber replicas. The experimental data were analyzed using the Persson contact mechanics and rubber friction theory. [ABSTRACT FROM AUTHOR]